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Reconstruction of changes in the Amundsen Sea and BellingshausenSea sector of the West Antarctic Ice Sheet since the Last GlacialMaximum
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2013 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 100, 56-86 p.Article in journal (Refereed) Published
Abstract [en]

Marine and terrestrial geological and marine geophysical data that constrain deglaciation since the LastGlacial Maximum (LGM) of the sector of theWest Antarctic Ice Sheet (WAIS) draining into the AmundsenSea and Bellingshausen Sea have been collated and used as the basis for a set of time-slice reconstructions.The drainage basins in these sectors constitute a little more than one-quarter of the area ofthe WAIS, but account for about one-third of its surface accumulation. Their mass balance is becomingincreasingly negative, and therefore they account for an even larger fraction of currentWAIS discharge. Ifall of the ice in these sectors of the WAIS were discharged to the ocean, global sea level would rise byca 2 m.There is compelling evidence that grounding lines of palaeo-ice streams were at, or close to, thecontinental shelf edge along the Amundsen Sea and Bellingshausen Sea margins during the last glacialperiod. However, the few cosmogenic surface exposure ages and ice core data available from the interiorofWest Antarctica indicate that ice surface elevations there have changed little since the LGM. In the fewareas from which cosmogenic surface exposure ages have been determined near the margin of the icesheet, they generally suggest that there has been a gradual decrease in ice surface elevation since pre-Holocene times. Radiocarbon dates from glacimarine and the earliest seasonally open marine sedimentsin continental shelf cores that have been interpreted as providing approximate ages for post-LGMgrounding-line retreat indicate different trajectories of palaeo-ice stream recession in the Amundsen Seaand Bellingshausen Sea embayments. The areas were probably subject to similar oceanic, atmosphericand eustatic forcing, in which case the differences are probably largely a consequence of how topographicand geological factors have affected ice flow, and of topographic influences on snow accumulation andwarm water inflow across the continental shelf.Pauses in ice retreat are recorded where there are “bottle necks” in cross-shelf troughs in both embayments.The highest retreat rates presently constrained by radiocarbon dates from sediment cores arefound where the grounding line retreated across deep basins on the inner shelf in the Amundsen Sea,which is consistent with the marine ice sheet instability hypothesis. Deglacial ages from the Amundsen 

Sea Embayment (ASE) and Eltanin Bay (southern Bellingshausen Sea) indicate that the ice sheet hadalready retreated close to its modern limits by early Holocene time, which suggests that the rapid icethinning, flow acceleration, and grounding line retreat observed in this sector over recent decades areunusual in the context of the past 10,000 years.

Place, publisher, year, edition, pages
2013. Vol. 100, 56-86 p.
Keyword [en]
Ice sheet, Last Glacial Maximum, Holocene, Ice stream, Grounding line, Radiocarbon, Cosmogenic isotope, Surface exposure age, Multibeam swath bathymetry, Sediment, Glacimarine, Diamicton, Continental shelf, Circumpolar deep water, Subglacial meltwater, Sea level
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URN: urn:nbn:se:su:diva-98027DOI: 10.1016/j.quascirev.2013.10.016OAI: diva2:682202
Swedish Research Council
Available from: 2013-12-25 Created: 2013-12-25 Last updated: 2014-09-09Bibliographically approved

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Jakobsson, Martin
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Department of Geological Sciences
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